FISH COMMISSION OF THE UNITED STATES. 259 



fathom in circumference, so that the number of turns gave the 

 quantity of line ran out. Sometimes the soundings were repeated 

 in order to test their correctness, and in depths of 1,500 to 2,000 

 fathoms the results have agreed to within a fathom. 



As regards the distribution of life between the surface and the 

 bottom, the " Challenger" observations would show that down to 1,000 

 fathoms there appeared to be no zone where life did not exist, but on 

 further investigation it seems that these results are not to be depended 

 nj)on as conclusive, because as the tow-net goes down and comes 

 Up again it collects organisms from all depths, and it is not 

 possible, therefore, to say whether its contents come from the bottom 

 or not. This difficulty was understood and acknowledged, but for 

 some time nothing was done to remedy it, until Captain Sigsbee 

 devised what was called a "water trap" for the purpose. This 

 consists of a coj^per cylinder, with a valve at the bottom opening 

 upwards, and a strainer at the top. It is so arranged that it 

 can be let down to any desired depth, and then, by opening the 

 valve, a sample of the water at that depth is secured. The sinker 

 is first attached to the line in the usual way, and let down to a 

 convenient distance, and a metal stop fixed upon the wire. The 

 " water trap " is then put upon the wire about 50 fathoms higher 

 up, with its valve closed, and the interior filled with water which 

 has been previously strained. The line is next run out until the stop 

 reaches the depth it is desired to examine. 



A metal plate is now let down [the line, and this, by striking 

 the water trap, opens the bottom valve, and at the same time 

 releases the cylinder, which then runs down the line until it reaches 

 the stop, which arrests its descent, and at the same time closed the 

 valve again. 



On drawing the trap once more to the surface they can be sure 

 that the water inside has been taken in from between the points 

 where the valve was opened and where it was again closed. 



By these means they have found reasons for concluding that life 

 is confined to a zone near the surface and to another near the 

 bottom, a fact of great interest to those who study the Forami- 

 nifera and the Polycistinee, and a fact which would also naturally 

 refute some of the conclusions of Sir Wyville Thomson. The 

 entire absence of organic remains at the greatest depths has yet to 

 be fully explained. It has been supposed that they become 

 dissolved, but this difficulty remains, that large quantities of 



